One of the most important goals of parents and educators of youth with Down syndrome (DS) is to promote the highest degree of independent living that is possible. Available evidence indicates that persons with DS exhibit a particular weakness in wayfinding, a complex spatial skill that is associated with learning, reproducing, and thinking about means for navigating the environment (e.g., Benson, Merrill, & Conners, 2009; Benson, Merrill, Conners, & Roskos, 2011). This weakness is consistent with parental reluctance to allow their adult children with DS to travel beyond the boundaries of their own property (Carr, 2008), thereby impacting the degree of independent functioning they have in everyday life activities. A recently completed R03 awarded to the primary investigators of this application revealed a particular weakness in acquiring route knowledge by youth with DS. However, when exploring an environment, most people also acquire survey knowledge; that is, knowledge about the spatial configuration of the environment. Survey knowledge represents an overview of the spatial environment in terms of relative locations of various features of the spatial layout. Hence, survey knowledge is a more flexible form of knowledge that permits individuals to navigate from one location to another following routes that have not been directly experienced when, for example, known routes are blocked (in the case of detours) or short cuts are available based on an individual's current location. We have identified a number of spatial and nonspatial abilities that have been found to directly impact performance in the complex skill of wayfinding for typically developing children and young adults. We view these as prerequisite enablers of wayfinding. In particular, the category of spatial abilities represents a seriously understudied domain of cognitive performance in DS. In this project, we systematically investigate the performance of persons with DS on four measures of basic spatial abilities and two complex spatial skills associated with wayfinding/navigation activities (i.e., acquiring route knowledge and acquiring survey knowledge of large scale environments). Based on the pattern of group differences in basic abilities we observe and the pattern of relationships between these abilities and wayfinding performance we obtain, we hope to be able to devise means for facilitating wayfinding performance in persons with DS. Hence, our ultimate goals are to identify those basic abilities that are especially deficient and need to be trained in persons with DS to enable general wayfinding activities and, if necessary, teach persons with DS how to use those abilities in support of efficient wayfinding. A secondary purpose is to attempt to identity, throug evaluating the pattern of relationships we observe, alternate and potentially easier to learn means to acquiring effective wayfinding skills in persons with DS.